Summary:
ShiA has been implicated in the high affinity transport of shikimate, an intermediate in the aromatic amino acid biosynthetic pathway [Whipp98, Brown76a]. Chromosomal mutants in shiA are unable to transport shikimate, and introduction of the cloned shiA gene restores shikimate transport [Whipp98]. The ShiA protein has twelve predicted TMS and is a member of the major facilitator superfamily of transporters (MFS) [Pao98] and hence is likely to function as a proton/shikimate symporter. Analysis of a shiA-lacZ fusion has suggested that shiA expression is constitutive and is not regulated by the TyrR repressor [Whipp98]. The shiA gene probably constitutes a monocistronic operon. Imported shikimate presumably serves as a substrate for biosynthesis of aromatic compounds.